pdb归档日志无法删除

PDB SEED（种子 PDB）通常以只读模式打开，只有在执行 Oracle 数据库补丁的数据补丁时才会更新scn，这样会导致PDB SEED备份要比其他数据文件的scn小，为了保证恢复，归档日志会一直保留，即使已经超过了保留时间依然无法删除。

解决办法：

$ cat reopen_seed.sql
alter session set container = PDB$SEED;
alter session set "_oracle_script"=TRUE;
alter pluggable database PDB$SEED close immediate;
alter pluggable database PDB$SEED open read write;
alter pluggable database PDB$SEED close;
alter pluggable database PDB$SEED open read only;
exit; 

$ cat REOPEN_SEED.sh
#/bin/bash
source .bashrc
sqlplus / as sysdba @reopen_seed.sql
exit

0级备份前执行一次，保证sedd能正常更新scn

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